What is Sound?

Sound is in air, sound is in water, sound is in metal and sound is in wood. Sound is waves or vibrations that our ears comprehend if they fall within a certain range of speed. The speed of the vibrations, the frequency, is described in Hertz (Hz). When we are young, we can hear vibrations between 20 and 20,000 Hz but our hearing weakens with age. Many other living creatures such as dogs and bats, for example, hear much faster vibrations; frequencies that no longer exist as sounds to us. Human beings hear best in the region of approximately 3,000 Hz.

We typically think of sound as vibrations in the air, and this is most often the case. But vibrations are found in other places as well; take a tuning fork, strike it and place it against your skull. You will hear a tone, but it does not enter your head through the air, but through the bone in your skull. Other types of vibrations are slower, such as those found in most cars; deep humming sounds that makes many people drowsy when they drive.

Sound is most often transported in the air and is heard through the ears. The ear is the most complicated mechanical part of the body, and it is in the ear that the soundwaves start to make sense - the sound is "taken apart."

When we speak of sound, acoustics is a term that is often used. Sound consists of any vibrations that are started somewhere - in a throat, a loudspeaker, a bell tower or an airplane engine. But the sound is reflected when it hits something, reacting differently depending on the kind of surface it meets. Some materials "absorb" sound and very little bounces back, while other materials reflect more. You may try listening to the difference between, for example, shouting at a concrete wall and then at a soft curtain. The curtain absorbs more and reflects less.

All spaces have their own acoustics, and reverberation is a term that describes the sounds that are reflected back and forth within a space. This is an important consideration when building a room where music will be played, or a space where it is important that speech be understood clearly.

Amplitude, how loud a sound is, describes an aspect of sound as well. A sound's volume is measured in decibel (dB), and there is a level at which sound becomes painful to our ears; approx. 120 dB. While sounds that are loud are generally heard better, what we hear best are those things that we are interested in hearing. Parents often recognize the voices of their own children in a group of children that are playing, laughing and shouting. Neither can the ears be "turned off" like our eyes. Shout into the ear of a sleeping person and she awakes - wave a red flag in front of a sleeping person's eyes and the only thing that happens is that your arm will get tired. The exterior of the ear is shaped to assist in distinguishing whether what we hear is coming from behind or in front of us. The fact that we have two ears - our antennae - is important when making our way in traffic, for example.

These things tell us about sound in physical terms, but what sound makes us think about, or experience, is something else. The latter concerns music - organized sound. And if you don't organize sound, do you still have music?